Multi-licensing is the practice of distributing

software Software is a set of computer programs and associated documentation and data. This is in contrast to hardware, from which the system is built and which actually performs the work. At the lowest programming level, executable code consist ...

under two or more different sets of terms and conditions. This may mean multiple different

software license A software license is a legal instrument (usually by way of contract law, with or without printed material) governing the use or redistribution of software. Under United States copyright law, all software is copyright protected, in both sourc ...

s or sets of licenses. Prefixes may be used to indicate the number of licenses used, e.g. dual-licensed for software licensed under two different licenses. When software is multi-licensed, recipients can typically choose the terms under which they want to use or distribute the software, but the simple presence of multiple licenses in a software package or library does not necessarily indicate that the recipient can freely choose one or the other. In some cases, especially when the software has multiple origins, ''all'' the accompanied licenses apply at the same time. The applicability of the different licenses has to be individually checked. The distributor may or may not apply a fee to either option. The two usual motivations for multi-licensing are

license compatibility License compatibility is a legal framework that allows for pieces of software with different software licenses to be distributed together. The need for such a framework arises because the different licenses can contain contradictory requiremen ...

and

market segregation Market is a term used to describe concepts such as: *Market (economics), system in which parties engage in transactions according to supply and demand *Market economy *Marketplace, a physical marketplace or public market Geography *Märket, an ...

based business models.

Business models

Multi-licensing is commonly done to support

free software Free software or libre software is computer software distributed under terms that allow users to run the software for any purpose as well as to study, change, and distribute it and any adapted versions. Free software is a matter of liberty, n ...

business models in a commercial environment. In this scenario, one option is a proprietary software license, which allows the possibility of creating proprietary applications derived from it, while the other license is a

copyleft Copyleft is the legal technique of granting certain freedoms over copies of copyrighted works with the requirement that the same rights be preserved in derivative works. In this sense, ''freedoms'' refers to the use of the work for any purpose ...

open-source license An open-source license is a type of license for computer software and other products that allows the source code, blueprint or design to be used, modified and/or shared under defined terms and conditions. This allows end users and commercial com ...

, thus requiring any derived work to be released under the same license. The copyright holder of the software then typically provides the free version of the software at little or no cost, and profits by selling proprietary licenses to commercial operations looking to incorporate the software into their own business. This model can be compared to

shareware Shareware is a type of proprietary software that is initially shared by the owner for trial use at little or no cost. Often the software has limited functionality or incomplete documentation until the user sends payment to the software developer ...

. Since in most cases, only the copyright holder can change the licensing terms of a software, multi licensing is mostly used by companies that wholly own the software which they are licensing. Confusion may arise when a person outside the company creates additional source code, using the less restrictive license. Because the company with the official code is not the copyright holder of the additional code, they may not legally include this new work in their more restrictively licensed version. Companies may require outside developers agree to a contributor license agreement before accepting their work in the official code-base and source code repositories. Multi licensing is used by the copyright holders of some

packages advertising their willingness to distribute using both a

free software license and a non-free software license. The latter license typically offers users the software as

proprietary software Proprietary software is software that is deemed within the free and open-source software to be non-free because its creator, publisher, or other rightsholder or rightsholder partner exercises a legal monopoly afforded by modern copyright and i ...

or offers third parties the source code without copyleft provisions. Copyright holders are exercising the monopoly they're provided under

copyright A copyright is a type of intellectual property that gives its owner the exclusive right to copy, distribute, adapt, display, and perform a creative work, usually for a limited time. The creative work may be in a literary, artistic, educatio ...

in this scenario, but also use multi licensing to distinguish the rights and freedoms different recipients receive. Such licensing allows the holder to offer customizations and early releases, generate other derivative works or grant rights to third parties to redistribute proprietary versions all while offering everyone a free version of the software. Sharing the package as copyleft free software can benefit the copyright holder by receiving contributions from users and hackers of the

free software community The free software movement is a social movement with the goal of obtaining and guaranteeing certain freedoms for software users, namely the freedoms to run the software, to study the software, to modify the software, and to share copies of the s ...

. These contributions can be the support of a dedicated user community,

word of mouth Word of mouth, or ''viva voce'', is the passing of information from person to person using oral communication, which could be as simple as telling someone the time of day. Storytelling is a common form of word-of-mouth communication where one pe ...

marketing or modifications that are made available as stipulated by a copyleft license. However, a copyright holder's commitment to elude copyleft provisions and advertise proprietary redistributions risks losing confidence and support from free software users. Examples of multi-licensed software include

Oracle An oracle is a person or agency considered to provide wise and insightful counsel or prophetic predictions, most notably including precognition of the future, inspired by deities. As such, it is a form of divination. Description The word ...

's NetBeans IDE,

MySQL AB MySQL AB was a Swedish software company founded in 1995. It was acquired by Sun Microsystems in 2008, Sun was in turn acquired by Oracle Corporation in 2010. MySQL AB is the creator of MySQL, a relational database management system, as well as ...

's database,

Asterisk The asterisk ( ), from Late Latin , from Ancient Greek , ''asteriskos'', "little star", is a typographical symbol. It is so called because it resembles a conventional image of a heraldic star. Computer scientists and mathematicians often voc ...

Oracle Corporation Oracle Corporation is an American multinational computer technology corporation headquartered in Austin, Texas. In 2020, Oracle was the third-largest software company in the world by revenue and market capitalization. The company sells da ...

Berkeley DB Berkeley DB (BDB) is an unmaintained embedded database software library for key/value data, historically significant in open source software. Berkeley DB is written in C with API bindings for many other programming languages. BDB stores arbitr ...

, Modelio, ZeroC's Ice, Magnolia CMS, JUCE, wolfSSL, and Qt Software's Qt development toolkit. Description on one specific example to illustrate multi-licensing: Oracle MySQL comes in various editions: MySQL Enterprise Edition is a commercial edition, hence to be purchased. The license is only offered as a subscription, named MySQL Enterprise Edition Subscription. The same applies for MySQL Standard Edition (MySQL Standard Edition Subscription) and MySQL Cluster CGE (MySQL Cluster Carrier Grade Edition Subscription). The other editions, such as the MySQL Classic Edition or MySQL Community Edition, are free to use with some restrictions. For instance, the MySQL Community Edition is a freely downloadable version, available under the GPL license and is supported by a community of open source developers.

Single-vendor commercial open source business model

The term ''single-vendor commercial open source'' was coined by Dirk Riehle in 2010, and has later been further popularized by other scholars, such as

Simon R. B. Berdal Simon may refer to: People * Simon (given name), including a list of people and fictional characters with the given name Simon * Simon (surname), including a list of people with the surname Simon * Eugène Simon, French naturalist and the genus ...

. According to Riehle: In contrast to traditional open source projects, a single-vendor commercial open source project ''is controlled by exactly one stakeholder with the purpose of commercially exploiting it''. In this context, the open source community is less engaged in the development of core functionality, as they typically are in conventional (pure) open source projects. As the then CEO Mårten Mikos of

MySQL MySQL () is an open-source relational database management system (RDBMS). Its name is a combination of "My", the name of co-founder Michael Widenius's daughter My, and "SQL", the acronym for Structured Query Language. A relational database ...

said in an interview: Hence, the community of multi-license software as a rule includes employees of the code-owning firm, as well as strategic partners that have vested interest in the software. As Riehle notes, ''In single-vendor open source, almost all of the core product development work is carried out by the commercial firm, with occasional contributions from the community.'' As Berdal notes, the governance of the open source community becomes ''a key business management process'' in this context: ''As such, it needs to be aligned with other business activities. Governance models of dual-licensed OSS editions may therefore display a tendency towards commercial bias. To prevent the community from being provoked or alienated it may therefore seem imperative to balance commercial inclinations against “open” interests.'' This is by no means an easy task. As Berdal demonstrated through a case study of

SugarCRM SugarCRM is a software company based in Silicon Valley. It produces the on-premises and cloud-based web application Sugar, a customer relationship management (CRM) system. SugarCRM's functionality includes sales-force automation, marketing cam ...

, this commercial open source software (COSS) business model can trigger substantial friction points, which can eventually lead to pure open source

forks In cutlery or kitchenware, a fork (from la, furca 'pitchfork') is a utensil, now usually made of metal, whose long handle terminates in a head that branches into several narrow and often slightly curved tines with which one can spear foods eit ...

(table adapted from Berdal, Table 3, page 75): Only a few months after these friction points were observed, a new fork of the

Community Edition was announced.

License compatibility

A second use of multi-licensing with free software is for

, allowing code from differently licensed free software projects to be combined, or to provide users the preference to pick a license. Examples include the

source code In computing, source code, or simply code, is any collection of code, with or without comments, written using a human-readable programming language, usually as plain text. The source code of a program is specially designed to facilitate the ...

Mozilla Application Suite The Mozilla Application Suite (originally known as Mozilla, marketed as the Mozilla Suite) is a discontinued cross-platform integrated Internet suite. Its development was initiated by Netscape Communications Corporation, before their acquisition ...

and previously

Mozilla Thunderbird Mozilla Thunderbird is a free and open-source cross-platform email client, personal information manager, news client, RSS and chat client developed by the Mozilla Foundation and operated by subsidiary MZLA Technologies Corporation. The projec ...

and

Mozilla Firefox Mozilla Firefox, or simply Firefox, is a free and open-source web browser developed by the Mozilla Foundation and its subsidiary, the Mozilla Corporation. It uses the Gecko rendering engine to display web pages, which implements current an ...

, that have used tri-licensing under the

Mozilla Public License The Mozilla Public License (MPL) is a free and open-source weak copyleft license for most Mozilla Foundation software such as Firefox and Thunderbird The MPL license is developed and maintained by Mozilla, which seeks to balance the conce ...

(MPL) 1.1,

GNU General Public License The GNU General Public License (GNU GPL or simply GPL) is a series of widely used free software licenses that guarantee end users the four freedoms to run, study, share, and modify the software. The license was the first copyleft for general ...

(GPL) 2.0 or

GNU Lesser General Public License The GNU Lesser General Public License (LGPL) is a free-software license published by the Free Software Foundation (FSF). The license allows developers and companies to use and integrate a software component released under the LGPL into their own ...

(LGPL) 2.1 before the latter upgraded to GPL-compatible MPL 2.0, making the tri-licensing unnecessary. Other examples are

Perl Perl is a family of two high-level, general-purpose, interpreted, dynamic programming languages. "Perl" refers to Perl 5, but from 2000 to 2019 it also referred to its redesigned "sister language", Perl 6, before the latter's name was offic ...

, which is dual-licensed under the GPL or

Artistic License Artistic license (alongside more contextually-specific derivative terms such as poetic license, historical license, dramatic license, and narrative license) refers to deviation from fact or form for artistic purposes. It can include the alterat ...

, and

Ruby A ruby is a pinkish red to blood-red colored gemstone, a variety of the mineral corundum ( aluminium oxide). Ruby is one of the most popular traditional jewelry gems and is very durable. Other varieties of gem-quality corundum are called ...

, whose

license A license (or licence) is an official permission or permit to do, use, or own something (as well as the document of that permission or permit). A license is granted by a party (licensor) to another party (licensee) as an element of an agreeme ...

contains explicit GPL dual licensing.

Market segregation in proprietary software

Multi-licensing is also used by distributors of non-free software. Sometimes this is done to proprietary software to segregate a market. By splitting customers into multiple categories such as home users, professional users, and academic users, copyright holders can set different prices for each group. However, among proprietary software companies, it is more common to release a "home edition" and a "professional edition" of a given product, which differ by the software and software features included, not just the license.

References

External links

Dual Licensing information
from OSS Watch * Article
The Dual-Licensing Model
May 1, 2002 by Don Marti * Article

Nov 16 2004 by Philip H. Albert * Article
Does dual licensing threaten free software?
Jul 27 2006 by Glyn Moody * Article

by Heather Meeker * Paper
Dual Licensing in Open Source Software Industry
by Mikko Välimäki

*

by Software Freedom Law Center * {{webarchive , date=2013-01-03 , url=https://archive.today/20130103212500/http://www.linuxdevices.com/news/NS8384267091.html , title=Combining GPL, closed code
Glossary of Software Licensing
Software licenses Terms of service